Production of metals



United States Patent 3,357,825 PRODUCTION OF METALS Richard W. Douglass, Needham, Mass., assignor to National Research Corporation, Cambridge, Mass., a corporation of Massachusetts No Drawing. Filed Jan. 11, 1965, Ser. No. 424,802

. 2 Claims. (Cl. 75-172) This application relates to the production of metals and more particularly to metals of the platinum group, e.g. platinum, rhodium, palladium and iridium and their alloys.

The principal object of the present invention is to provide an improved platinum group metal alloy having increased recrystallization temperature and increased resistance to grain growth at elevated temperatures.

Another object of the invention is to provide an improved alloy of the platinum group metals having improved grain structure and creep resistance.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the products possessing the features, properties, and the relation of components and the process involving the several steps and the relation and order of one or more of such steps with respect to each of the others which are exemplified in the following detailed disclosure and the scope of the application of which will be indicated in the claims.

Platinum group metals and alloys thereof have been utilized in certain high temperature systems Where their inertness has been unmatched by other alloys. However, a serious problem with such precious metals has been the tendency of such alloys to recrystallize and undergo substantial grain growth, at elevated temperatures. When thin sections are involved, grain growth can be extremely detrimental to the mechanical strength of the precious metal structure. This is particularly true when the growth is sufiicient to extend completely across the structural section and rupture along the grain boundary is most apt to occur.

In accordance with this invention, grain growth in the platinum group metals, platinum, palladium, iridium and rhodium has been substantially inhibited by the addition of small, but effective, quantities of yttrium. The yttrium is added as pure metal, preferably in an amount less than 1% of yttrium. When percentages are used in the specification, weight percent is intended.

In order that the invention may be more fully understood, reference should be had to the following nonlimiting examples:

Example 1 A series of platinum alloys was prepared from high purity oxygen-free platinum. The alloys were prepared by are melting 10 gram buttons containing the indicated weight percent of yttrium. Each alloy was melted three times and turned top to bottom for each melting. Compositions, fabrication and annealing schedules are given below in Table I.

TABLE I Alloy Fabrication Procedure One Hour Annealing and Result Temperatures, 0.

Platinum. Cold rolled to 0.020 750 1, 000 1, 250 1, 500

sheet, excellent.

Pt0.05Y- do 750 1, 000 1,250 1, 500 Pt-0.2Y d0 750 1, 000 1,250 1, 500 Pt-lY d0 1, 250 l, 500

1 This is used to describe the quality of the finished sheet and to indicate that iabricability was not impaired by processing and/or alloying.

Example 2 A similar series of palladium alloys was made. In this case high purity palladium powder was employed. The details are set forth in Table II.

Similar alloys were made using iridium and .2 weight percent yttrium and annealed at various temperatures.

Example 4 Two alloys were made; one of pure rhodium and the other containing .1 weight percent yttrium added to rhodium and annealed at several temperatures,

The above series of alloys, Examples 14, were tested and the rnicrostructure was examined after annealing at specified temperatures. The results are given in Table III below.

TABLE III [Microstructure after annealing at indicated temperature, (3.

Alloy I 750 I 800 1 R means recrystallized; NR means not recrystallized; numbers are AS'IM grain size numbers.

3 Example 5 Table IV ASTM Grain Size after Annealing at the Indicated Temperature 1,200" c. 1,300 C. 1,400 C.

Pt-13Rh 4-5 1 1 Pt-13Rh-0.2Y 7 5 4 A substantial grain refinement is achieved by use of small quantities of yttrium in platinum and other precious metals and alloys. These greatly increase the utility of such precious metals and alloys for high temperature use.

Since certain changes may be made in the above product without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A wrought platinum alloy having a fine grain structure and being resistant to grain coarsening upon annealing, said alloy consisting essentially of platinum and between about .05 and about .2 weight percent yttrium, said alloy being essentially free of oxygen.

2. A wrought precious metal alloy having a fine grain structure and being resistant to grain coarsening upon annealing, said alloy consisting essentially of latinum and about 13 Weight percent of one of the precious metals palladium, iridium and rhodium and between about .05 and about .2 weight percent yttrium, said alloy being essentially free of oxygen.

References Cited UNITED STATES PATENTS 7/ 1965 Betteridge et al 172 OTHER REFERENCES DAVID L. RECK, Primary Examiner.

H. F. SAITO, Assistant Examiner. 

1. A WROUGHT PLATINUM ALLOY HAVING A FINE GRAIN STRUCTURE AND BEING RESISTANT TO GRAIN COARSENING UPON ANNEALING, SAID ALLOY CONSISTING ESSENTIALLY OF PLATINUM AND BETWEEN ABOUT .05 AND ABOUT .2 WEIGHT PERCENT YTTRIUM, SAID ALLOY BEING ESSENTIALLY FREE OF OXYGEN. 